Aqueous Solutions of Acids and Alkalies. 



445 



Observations on the Table of Anhydrous Potash. 



The strongest solution of potash that I could prepare at 

 the temperature of 62° F. had the sp. gr. of 1*5607. Its che- 

 mical strength was 810°. This was determined by neutrali- 

 zation with pure sulphuric acid of 100°. Its formula is 

 KO, 6|H 2 0. According to Karsten the specific gravity of 

 anhydrous potash is about 2*656, which gives 31*73 septems 

 for the volume of the test atom ; but Dalton's specific gravity 

 of the hydrate of potash gives the very same number for the 

 volume of anhydrous potash. As it is improbable that pot- 

 ash and watefTwould combine to form the first hydrate with- 

 out condensation, I conclude that Karsten has merely calcu- 

 lated 'the specific gravity of anhydrous potash from the 

 specific gravity of the hydrate. 



The condensation effected by potash is considerable, nearly 

 approaching to that effected by sulphuric acid. In a solution 

 of 1° the condensation per atom is 93 septems, being three 

 times the measure of the anhydrous potash which causes it. 



The fraction which + 1 indicates the mean specific gravity 

 of 100° of potash is (l-656-^31'516 = ) -052545. 



Table XI. Showing the increase of Specific Gravity occa- 

 sioned in Solutions of KO by condensation. 



The greatest chemical strength, the greatest density, and 

 the greatest condensation in solutions of potash, all coincide. 

 In this particular potash agrees with soda, and with the two 

 fixed alkaline carbonates, but disagrees with the four acids. 

 The above table shows indeed rather more condensation in a 

 solution of 800° than in a solution of 810°, but the difference 

 falls within the limits of errors of experiment. It is difficult to 

 determine the specific gravity of a solution of potash saturated 

 at 62° F., because in cooling down a hot saturated solution an 

 abundant crystallization occurs at about 64° F., which raises 

 the temperature to above 70° F. If the solution is not well- 

 shaken, an excess of potash remains in it at 62° F. If the 

 temperature is allowed to descend a little lower than 62° F., 

 too much potash precipitates. The saturated solutions of 

 caustic soda, carbonate of soda, and carbonate of potash pos- 

 sess similar properties. All these substances crystallize with 

 facility when in saturated solutions at 62° F. It is therefore 

 very difficult to determine the point of saturation. 



